• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.673-674
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• 2006

The influence of several experimental parameters on the formation of stable Alloy 625 nanoparticles dispersion in ethanol was investigated. Several analyzing methods were applied, like transmission profiles measured by Turbiscan, transmission electron microscopy, X-ray diffraction, gas chromatography, and particle size analyzer. The correlation among the increase of particle sizes, caused by nanoparticle coalescence and collision, concentration of dispersant and time was presented and discussed. The optimum conditions for the formation of stable dispersion are evaluated.

• 상하수도학회지
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• 제12권4호
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• pp.53-58
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• 1998

Dissolved Air flotation (DAF) has become increasingly important in the field of drinking water treatment, however, the research to investigate the mechanism of collision between bubble and particle has been limited. The electrostatic repulsion forces between them are critical to collide with each other. Zetapotential of bubble and particle show their electrostatic condition. In this research, a setup to measure the zetapotential of rising microbubble is made using electrophoresis method and measured ZP of bubble in our Lab. The results show the effect of pH on zetapotential of bubble. The findings from this research are compared with other results. It will he helpful to understand and explain the mechanism of collisions between bubble and particle on different conditions of bubble charge in DAF process.

• 한국기계가공학회지
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• 제18권3호
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• pp.59-65
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• 2019

In many industries, particle packing is adopted quite frequently. In the particle packing process, the Discrete Element Method (DEM) can analyze the multi-collision of particles efficiently. Two types of contact models are frequently used for the DEM. One is the linear spring model, which has the fastest calculation time, and the other is the Hertz-Mindlin model, which is the most frequently used contact model employing the DEM. Meanwhile, very tiny particles in the micrometer order are used in modern industries. In the micro length order, surface force is important to decreased particle size. To consider the effect of surface force in this study, we performed a simulation with the Hertz-Mindlin model and added the Johnson-Kendall-Roberts (JKR) theory depicting surface force with surface energy. In addition, three contact models were compared with several parameters. As a result, it was found that the JKR model has larger residual stress than the general contact models because of the pull-off force. We also validated that surface force can influence particle behavior if the particles are small.

• 한국물환경학회지
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• 제35권1호
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• pp.64-71
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• 2019

In recent years, carbon dioxide ($CO_2$) bubbles emerged as the most widely applied material with the recycling of sequestrated storage to decrease global warming. Flotation using $CO_2$ as an alternative to air could be effective in overcoming the high power consumption in the dissolved air flotation (DAF) process. The comparison of DAF and DCF system indicated that, the carbon dioxide flotation (DCF) system with pressurized $CO_2$ only requires 1.5 ~ 2.0 atm, while the DAF system requires 3.0 ~ 6.0 atm. In a bid to understand the characteristics of particle separation, the single collector collision (SCC) model was used and a series of simulations were conducted to compare the differences of collision and flotation between $CO_2$ bubbles and air bubbles. In addition, laboratory experiments were sequentially done to verify the simulation results of the SCC model. Based on the simulation results, surfactant injection, which is known to decrease bubble size, cloud improved the collision efficiency of $CO_2$ bubbles similar to that of air bubbles. Furthermore, the results of the flotation experiments showed similar results with the simulation of the SCC model under anionic surfactant injection. The findings led us to conclude that $CO_2$ bubbles can be an alternative to air bubbles and a promising material as a collector to separate particles in the water and wastewater.

• Computers and Concrete
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• 제16권6호
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• pp.933-961
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• 2015

Damage by high-speed impact fracture is a dominant mode of failure in several applications of concrete structures. Numerical modelling can play a crucial role in understanding and predicting complex fracture processes. The commonly used mesh-based Finite Element Method has difficulties in accurately modelling the high deformation and disintegration associated with fracture, as this often distorts the mesh. Even with careful re-meshing FEM often fails to handle extreme deformations and results in poor accuracy. Moreover, simulating the mechanism of fragmentation requires detachment of elements along their boundaries, and this needs a fine mesh to allow the natural propagation of damage/cracks. Smoothed Particle Hydrodynamics (SPH) is an alternative particle based (mesh-less) Lagrangian method that is particularly suitable for analysing fracture because of its capability to model large deformation and to track free surfaces generated due to fracturing. Here we demonstrate the capabilities of SPH for predicting brittle fracture by studying a slender concrete structure (column) under the impact of a high-speed projectile. To explore the effect of the projectile material behaviour on the fracture process, the projectile is assumed to be either perfectly-elastic or elastoplastic in two separate cases. The transient stress field and the resulting evolution of damage under impact are investigated. The nature of the collision and the constitutive behaviour are found to considerably affect the fracture process for the structure including the crack propagation rates, and the size and motion of the fragments. The progress of fracture is tracked by measuring the average damage level of the structure and the extent of energy dissipation, which depend strongly on the type of collision. The effect of fracture property (failure strain) of the concrete due to its various compositions is found to have a profound effect on the damage and fragmentation pattern of the structure.

• 반도체디스플레이기술학회지
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• 제7권4호
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• pp.29-33
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• 2008

Rapid increase of integrity for recent semiconductor industry highly demands the development of removal technology of contaminated particles in the scale of a few microns or even smaller. It is known that the surface cleaning technology using $CO_2$ snow has its own merits of high efficiency. However, the detailed removal mechanism of particles using this technology is not yet fully understood due to the lack of sophisticated research endeavors. The detachment mechanism of particles from the substrates is known to be belonged in four types; rebounding, sliding, rolling and lifting. In this study, a modeling effort is performed to explain the detachment mechanism of a contaminant particle due to the rebounding caused by the vertical collision of the $CO_2$ snow. The Hertz and Johnson-Kendall-Roberts(JKR) theories are employed to describe the contact, adhesion and deformation mechanisms of the particles on a substrate. Numerical simulations are followed for several representative cases, which provide the perspective views on the dynamic characteristics of the particles as functions of the material properties and the initial inter-particle collision velocity.

• 상하수도학회지
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• 제19권2호
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• pp.161-172
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• 2005

Recently, water treatment methods utilizing microbubbles such as DAF and EF are gaining interest and being studied. Current study is focused on the fundamental research of electroflotation by examining the characteristics of microbubbles and particles. The objects of this research consist of two things; (1) theoretical modeling of microbubble-particle collision, (2) the experimental investigation of removal efficiency of turbidity in electroflotation. From investigation, the mechanism of electroflotation can be explained not only by the characteristics of microbubbles and particles but also the chemistry of aluminum dissolved from aluminum electrode during the electroflotation experiment.

• 한국가시화정보학회지
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• 제20권3호
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• pp.74-85
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• 2022

We propose a Cubic-Interpolated Pseudo-Particle Lattice Boltzmann method (CIP-LBM) for the convection-diffusion equation (CDE) based on the Bhatnagar-Gross-Krook (BGK) scheme equation. The CIP-LBM relies on an accurate numerical lattice equilibrium particle distribution function on the advection term and the use of a splitting technique to solve the Lattice Boltzmann equation. Different schemes of lattice spaces such as D1Q3, D2Q5, and D2Q9 have been used for simulating a variety of problems described by the CDE. All simulations were carried out using the BGK model, although another LB scheme based on a collision term like two-relation time or multi-relaxation time can be easily applied. To show quantitative agreement, the results of the proposed model are compared with an analytical solution.

• 대한화학회지
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• 제20권2호
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• pp.97-110
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• 1976

竝進-振動에너지 變換에 있어서 中間에너지 準位를 거치지 않는 直接勵起가 多量子 振動천이에 미치는 영향을 理論的으로 조사하였다. 衝突 모형은 直線 충돌이며, 分子間의 포텐셜은 指數函數型의 것을 振動좌표(q)로 전개하고 四次項 $(q^4)$까지 包含시켜 사용하였다. $q^2$, $q^3$, $q^4$를 포함시켰을 때의 천이 확률 $(P_{m{\rightarrow}n})$에 對한 一般式을 各各 유도하고, 몇개의 충돌계에 대하여 그 값들을 계산하였다.結果를 線型化시킨 포텐셜(q)을 사용한 경우의 結果와 比較하고 直按 多量子 振動遷移가 重要한 役割을 하게 되는 條件 파라미터 ${\nalpha}$ 및 m과 관련시켜 제시하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(2)
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• pp.21-24
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• 2001

We studied aluminum cluster deposition using molecular dynamics simulation. We investigated the variations of the cluster momentum and the impulse force during collisions, and found that the close-packed cluster impact has some of properties of the single particle collision and the linear chain collisions. We also simulated the series of energetic cluster deposition with energy Per atom. When energy Per atom in cluster has some eV rather than very low, the intermixing occurred easily in growth film and we can obtain a good film without subsequent annealing process.